Obviously not playing the right high ranks.
Jokes aside, against merkava, like luna said earlier you really have to inch your way forward, its a 50/50 battle once your in range of roll/assault. You either guess an anti-air command grab and roll, or guess the grounded command grab and assault. But once you can lock merkava down in a corner, hes yours since he has no REAL reversal option, and even then his ex236c trades almost 100% of the time if you meaty him with 5b.
For Gord it depends on the player, just learn their blockstrings and where they reverse beat and usually you can roll through one of his normals or projectile it. Otherwise cross your fingers and hope he doesn't shit on you.